Magnetic Relaxation in Iron Phthalocyanine Thin Films

Magnetism in thin films is a rich field. Ernst Ising solved the one-dimensional infinite magnetic chain theoretically. Even though he found no ferromagnetic to paramagnetic phase transition in 1D, this model became a paradigm system with tremendous educational value and various important applications. Yet, few experimental realizations were available until 2001, when single chain magnets were being investigated. Here, we present a system where the average chain length is tunable from 40 nm to 110 nm in iron phthalocyanine thin films. We study the temporal remnance curves. Collapsing temperature-dependent remnance measurements into a master curve is equivalent to year-long measurements of the remnance. The relaxation times follow an Arrhenius behavior and have a constant energy barrier of 95K. The single spin relaxation time strongly increases with chain length. This low-dimensional magnetic system is explained in detail.